Abstract

Advanced structural ceramics are those ceramics intended for use as load-bearing members. They are materials that combine the properties and advantages of traditional ceramics, such as chemical inertness, high temperature capability, and hardness, with the ability to carry a significant mechanical stress. Advanced structural ceramics are more expensive than traditional ceramics. Most of the advanced structural ceramics under development today are based on silicon nitride, Si₃N₄; silicon carbide, SiC; zirconia, ZrO₂; or alumina, Al₂O₃. Advanced structural ceramics typically possess some combination of high temperature capabilities, high strength, toughness or flaw tolerance, high hardness, mechanical strength retention at high temperatures, wear resistance, corrosion resistance, thermal shock resistance, creep resistance, and long-term durability. The relationship between processing and properties is especially critical for advanced structural ceramics because subsequent successful operation in severe environments often requires carefully controlled compositions and microstructures. Fabrication generally takes place in four steps: powder processing, consolidation/forming, densification, and finishing. The focus has been on applications for gas turbine, diesel, and spark-ignited engines. Advanced structural ceramics are also under investigation for use in numerous other high performance applications including metal-cutting and shaping tools, and various military applications. Exposure limits for silicon carbide and powders of zirconium compounds (including zirconium dioxide) have been established by ACGIH. The solid ceramics present no apparent health hazard.